Overall Ventilation System Flow Network Calculation for Site Recommendation Page: 4 of 90
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ANL-SFS-MG-000001, REV00 (CRWMS M&O 2000a). The airflow direction in a branch is
described by the sequence nodes are entered into the data file; the first node defines the start
point and the second node defines the end point. There is no error if the start/finish nodes are
entered backward in the data file, the VNETPC program simply assigns a negative value to any
airflow that is calculated as reverse of the node entry sequence.
A dummy branch may represent a surface connection, leakage path, fan recirculation path, or to
assist with the visual presentation of the airflow network. Dummy branches do not contain a
length, therefore no resistance (see Equation 1) is calculated. If a drift is represented by a series
of branches, including a dummy branch, the actual layout distance and airway characteristics are
included in one of the branches.
Fixed airflow quantity branches are used to hold a consistent airflow volume in a branch, or
adjacent to the main fans to provide the airflow through the repository.
Airway friction factors are assigned per Mine Ventilation and Air Conditioning (Hartman et al.
1997, Table 5.1). Fan locations and characteristic curves are provided as input data (Section
5.1.3). The finished airflow network represents a closed circuit of interconnected branches. The
input data file (Attachment I) contains the airway characteristic data for the airflow network and
provides the basis for the VNETPC calculation. There are no unique electronic data handling
requirements. Additional detail on the approach used for this calculation is included in Section
2.2 VNETPC PROGRAM OPERATION INFORMATION
This section describes how the VNETPC program performs a network calculation. The
VNETPC program allows the calculation to be made in either SI or Imperial units as described in
the VnetPC for Windows Version 1.Oa Users Manual (Mine Ventilation Services 1997, p. 5).
This calculation uses SI units with Imperial unit conversions provided in Section 6, Results.
The VNETPC program calculates the normal branch resistance R (N-s2/m) using Equation 1
(Hartman et al. 1997, p. 242).
R = KO(l+ le) Equation 1
Where: K= airway friction factor (dimensionless)
1= length, m
le = equivalent length, m
A = area, m2
O = Perimeter, m
The VNETPC program assumes an incompressible flow and is based on Kirchoff's Laws (Mine
Ventilation Services 1997, Section 2.1.1). The code utilizes an accelerated form of the Hardy
Cross iterative method to converge on a numerical solution of the airflow network. Kirchoff s
Laws assume an incompressible flow for which:
CAL-SVS-HV-000002 REV 00
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Steinhoff, Jeff J. Overall Ventilation System Flow Network Calculation for Site Recommendation, report, August 2, 2001; Las Vegas, Nevada. (digital.library.unt.edu/ark:/67531/metadc719973/m1/4/: accessed December 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.